Design of a double aging treatment for the improvement of mechanical and microstructural properties of pulse micro-plasma arc welded alloy 718

摘要

The effect of post-weld solution along with different double aging treatments on precipitation of various strengthening phases in Alloy 718 weld is carried out in the current assessment. The formation of intermetallic phases in the weld zone deteriorates the mechanical properties and quality of the weld joint. The high-temperature solution treatment at 1165 degrees C/1 h has dissolved the intermetallic phases and makes a suitable quantity of alloying elements accessible for precipitation of the strengthening phases. To analyze the impact of aging temperature and holding time on delta, gamma' and gamma" phase precipitation, four different heat treatment paths are designed. The heat treatment holding time is reduced by 53% on the welded component by applying a higher aging temperature compared to the conventional standard aging temperatures. The variation in aging temperature and holding time followed by solution treatment changes the platelet morphology of the delta phase to needle shape in the grain boundary. Significant enhancement in the tensile strength (21%) and weld hardness (121%) is witnessed due to duplex aging treatment compared to as-welded condition. The XRD analysis confirms the precipitation of gamma' and gamma'' strengthening phases inside the grain and delta particles in the grain boundaries.